// This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
// Copyright (C) 2018 Gael Guennebaud <gael.guennebaud@inria.fr>
//
// This Source Code Form is subject to the terms of the Mozilla
// Public License v. 2.0. If a copy of the MPL was not distributed
// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.

#ifndef EIGEN_STLITERATORS_H
#define EIGEN_STLITERATORS_H

namespace Eigen {

namespace internal {

    template <typename IteratorType> struct indexed_based_stl_iterator_traits;

    template <typename Derived> class indexed_based_stl_iterator_base
    {
    protected:
        typedef indexed_based_stl_iterator_traits<Derived> traits;
        typedef typename traits::XprType XprType;
        typedef indexed_based_stl_iterator_base<typename traits::non_const_iterator> non_const_iterator;
        typedef indexed_based_stl_iterator_base<typename traits::const_iterator> const_iterator;
        typedef typename internal::conditional<internal::is_const<XprType>::value, non_const_iterator, const_iterator>::type other_iterator;
        // NOTE: in C++03 we cannot declare friend classes through typedefs because we need to write friend class:
        friend class indexed_based_stl_iterator_base<typename traits::const_iterator>;
        friend class indexed_based_stl_iterator_base<typename traits::non_const_iterator>;

    public:
        typedef Index difference_type;
        typedef std::random_access_iterator_tag iterator_category;

        indexed_based_stl_iterator_base() EIGEN_NO_THROW : mp_xpr(0), m_index(0) {}
        indexed_based_stl_iterator_base(XprType& xpr, Index index) EIGEN_NO_THROW : mp_xpr(&xpr), m_index(index) {}

        indexed_based_stl_iterator_base(const non_const_iterator& other) EIGEN_NO_THROW : mp_xpr(other.mp_xpr), m_index(other.m_index) {}

        indexed_based_stl_iterator_base& operator=(const non_const_iterator& other)
        {
            mp_xpr = other.mp_xpr;
            m_index = other.m_index;
            return *this;
        }

        Derived& operator++()
        {
            ++m_index;
            return derived();
        }
        Derived& operator--()
        {
            --m_index;
            return derived();
        }

        Derived operator++(int)
        {
            Derived prev(derived());
            operator++();
            return prev;
        }
        Derived operator--(int)
        {
            Derived prev(derived());
            operator--();
            return prev;
        }

        friend Derived operator+(const indexed_based_stl_iterator_base& a, Index b)
        {
            Derived ret(a.derived());
            ret += b;
            return ret;
        }
        friend Derived operator-(const indexed_based_stl_iterator_base& a, Index b)
        {
            Derived ret(a.derived());
            ret -= b;
            return ret;
        }
        friend Derived operator+(Index a, const indexed_based_stl_iterator_base& b)
        {
            Derived ret(b.derived());
            ret += a;
            return ret;
        }
        friend Derived operator-(Index a, const indexed_based_stl_iterator_base& b)
        {
            Derived ret(b.derived());
            ret -= a;
            return ret;
        }

        Derived& operator+=(Index b)
        {
            m_index += b;
            return derived();
        }
        Derived& operator-=(Index b)
        {
            m_index -= b;
            return derived();
        }

        difference_type operator-(const indexed_based_stl_iterator_base& other) const
        {
            eigen_assert(mp_xpr == other.mp_xpr);
            return m_index - other.m_index;
        }

        difference_type operator-(const other_iterator& other) const
        {
            eigen_assert(mp_xpr == other.mp_xpr);
            return m_index - other.m_index;
        }

        bool operator==(const indexed_based_stl_iterator_base& other) const
        {
            eigen_assert(mp_xpr == other.mp_xpr);
            return m_index == other.m_index;
        }
        bool operator!=(const indexed_based_stl_iterator_base& other) const
        {
            eigen_assert(mp_xpr == other.mp_xpr);
            return m_index != other.m_index;
        }
        bool operator<(const indexed_based_stl_iterator_base& other) const
        {
            eigen_assert(mp_xpr == other.mp_xpr);
            return m_index < other.m_index;
        }
        bool operator<=(const indexed_based_stl_iterator_base& other) const
        {
            eigen_assert(mp_xpr == other.mp_xpr);
            return m_index <= other.m_index;
        }
        bool operator>(const indexed_based_stl_iterator_base& other) const
        {
            eigen_assert(mp_xpr == other.mp_xpr);
            return m_index > other.m_index;
        }
        bool operator>=(const indexed_based_stl_iterator_base& other) const
        {
            eigen_assert(mp_xpr == other.mp_xpr);
            return m_index >= other.m_index;
        }

        bool operator==(const other_iterator& other) const
        {
            eigen_assert(mp_xpr == other.mp_xpr);
            return m_index == other.m_index;
        }
        bool operator!=(const other_iterator& other) const
        {
            eigen_assert(mp_xpr == other.mp_xpr);
            return m_index != other.m_index;
        }
        bool operator<(const other_iterator& other) const
        {
            eigen_assert(mp_xpr == other.mp_xpr);
            return m_index < other.m_index;
        }
        bool operator<=(const other_iterator& other) const
        {
            eigen_assert(mp_xpr == other.mp_xpr);
            return m_index <= other.m_index;
        }
        bool operator>(const other_iterator& other) const
        {
            eigen_assert(mp_xpr == other.mp_xpr);
            return m_index > other.m_index;
        }
        bool operator>=(const other_iterator& other) const
        {
            eigen_assert(mp_xpr == other.mp_xpr);
            return m_index >= other.m_index;
        }

    protected:
        Derived& derived() { return static_cast<Derived&>(*this); }
        const Derived& derived() const { return static_cast<const Derived&>(*this); }

        XprType* mp_xpr;
        Index m_index;
    };

    template <typename Derived> class indexed_based_stl_reverse_iterator_base
    {
    protected:
        typedef indexed_based_stl_iterator_traits<Derived> traits;
        typedef typename traits::XprType XprType;
        typedef indexed_based_stl_reverse_iterator_base<typename traits::non_const_iterator> non_const_iterator;
        typedef indexed_based_stl_reverse_iterator_base<typename traits::const_iterator> const_iterator;
        typedef typename internal::conditional<internal::is_const<XprType>::value, non_const_iterator, const_iterator>::type other_iterator;
        // NOTE: in C++03 we cannot declare friend classes through typedefs because we need to write friend class:
        friend class indexed_based_stl_reverse_iterator_base<typename traits::const_iterator>;
        friend class indexed_based_stl_reverse_iterator_base<typename traits::non_const_iterator>;

    public:
        typedef Index difference_type;
        typedef std::random_access_iterator_tag iterator_category;

        indexed_based_stl_reverse_iterator_base() : mp_xpr(0), m_index(0) {}
        indexed_based_stl_reverse_iterator_base(XprType& xpr, Index index) : mp_xpr(&xpr), m_index(index) {}

        indexed_based_stl_reverse_iterator_base(const non_const_iterator& other) : mp_xpr(other.mp_xpr), m_index(other.m_index) {}

        indexed_based_stl_reverse_iterator_base& operator=(const non_const_iterator& other)
        {
            mp_xpr = other.mp_xpr;
            m_index = other.m_index;
            return *this;
        }

        Derived& operator++()
        {
            --m_index;
            return derived();
        }
        Derived& operator--()
        {
            ++m_index;
            return derived();
        }

        Derived operator++(int)
        {
            Derived prev(derived());
            operator++();
            return prev;
        }
        Derived operator--(int)
        {
            Derived prev(derived());
            operator--();
            return prev;
        }

        friend Derived operator+(const indexed_based_stl_reverse_iterator_base& a, Index b)
        {
            Derived ret(a.derived());
            ret += b;
            return ret;
        }
        friend Derived operator-(const indexed_based_stl_reverse_iterator_base& a, Index b)
        {
            Derived ret(a.derived());
            ret -= b;
            return ret;
        }
        friend Derived operator+(Index a, const indexed_based_stl_reverse_iterator_base& b)
        {
            Derived ret(b.derived());
            ret += a;
            return ret;
        }
        friend Derived operator-(Index a, const indexed_based_stl_reverse_iterator_base& b)
        {
            Derived ret(b.derived());
            ret -= a;
            return ret;
        }

        Derived& operator+=(Index b)
        {
            m_index -= b;
            return derived();
        }
        Derived& operator-=(Index b)
        {
            m_index += b;
            return derived();
        }

        difference_type operator-(const indexed_based_stl_reverse_iterator_base& other) const
        {
            eigen_assert(mp_xpr == other.mp_xpr);
            return other.m_index - m_index;
        }

        difference_type operator-(const other_iterator& other) const
        {
            eigen_assert(mp_xpr == other.mp_xpr);
            return other.m_index - m_index;
        }

        bool operator==(const indexed_based_stl_reverse_iterator_base& other) const
        {
            eigen_assert(mp_xpr == other.mp_xpr);
            return m_index == other.m_index;
        }
        bool operator!=(const indexed_based_stl_reverse_iterator_base& other) const
        {
            eigen_assert(mp_xpr == other.mp_xpr);
            return m_index != other.m_index;
        }
        bool operator<(const indexed_based_stl_reverse_iterator_base& other) const
        {
            eigen_assert(mp_xpr == other.mp_xpr);
            return m_index > other.m_index;
        }
        bool operator<=(const indexed_based_stl_reverse_iterator_base& other) const
        {
            eigen_assert(mp_xpr == other.mp_xpr);
            return m_index >= other.m_index;
        }
        bool operator>(const indexed_based_stl_reverse_iterator_base& other) const
        {
            eigen_assert(mp_xpr == other.mp_xpr);
            return m_index < other.m_index;
        }
        bool operator>=(const indexed_based_stl_reverse_iterator_base& other) const
        {
            eigen_assert(mp_xpr == other.mp_xpr);
            return m_index <= other.m_index;
        }

        bool operator==(const other_iterator& other) const
        {
            eigen_assert(mp_xpr == other.mp_xpr);
            return m_index == other.m_index;
        }
        bool operator!=(const other_iterator& other) const
        {
            eigen_assert(mp_xpr == other.mp_xpr);
            return m_index != other.m_index;
        }
        bool operator<(const other_iterator& other) const
        {
            eigen_assert(mp_xpr == other.mp_xpr);
            return m_index > other.m_index;
        }
        bool operator<=(const other_iterator& other) const
        {
            eigen_assert(mp_xpr == other.mp_xpr);
            return m_index >= other.m_index;
        }
        bool operator>(const other_iterator& other) const
        {
            eigen_assert(mp_xpr == other.mp_xpr);
            return m_index < other.m_index;
        }
        bool operator>=(const other_iterator& other) const
        {
            eigen_assert(mp_xpr == other.mp_xpr);
            return m_index <= other.m_index;
        }

    protected:
        Derived& derived() { return static_cast<Derived&>(*this); }
        const Derived& derived() const { return static_cast<const Derived&>(*this); }

        XprType* mp_xpr;
        Index m_index;
    };

    template <typename XprType> class pointer_based_stl_iterator
    {
        enum
        {
            is_lvalue = internal::is_lvalue<XprType>::value
        };
        typedef pointer_based_stl_iterator<typename internal::remove_const<XprType>::type> non_const_iterator;
        typedef pointer_based_stl_iterator<typename internal::add_const<XprType>::type> const_iterator;
        typedef typename internal::conditional<internal::is_const<XprType>::value, non_const_iterator, const_iterator>::type other_iterator;
        // NOTE: in C++03 we cannot declare friend classes through typedefs because we need to write friend class:
        friend class pointer_based_stl_iterator<typename internal::add_const<XprType>::type>;
        friend class pointer_based_stl_iterator<typename internal::remove_const<XprType>::type>;

    public:
        typedef Index difference_type;
        typedef typename XprType::Scalar value_type;
        typedef std::random_access_iterator_tag iterator_category;
        typedef typename internal::conditional<bool(is_lvalue), value_type*, const value_type*>::type pointer;
        typedef typename internal::conditional<bool(is_lvalue), value_type&, const value_type&>::type reference;

        pointer_based_stl_iterator() EIGEN_NO_THROW : m_ptr(0) {}
        pointer_based_stl_iterator(XprType& xpr, Index index) EIGEN_NO_THROW : m_incr(xpr.innerStride()) { m_ptr = xpr.data() + index * m_incr.value(); }

        pointer_based_stl_iterator(const non_const_iterator& other) EIGEN_NO_THROW : m_ptr(other.m_ptr), m_incr(other.m_incr) {}

        pointer_based_stl_iterator& operator=(const non_const_iterator& other) EIGEN_NO_THROW
        {
            m_ptr = other.m_ptr;
            m_incr.setValue(other.m_incr);
            return *this;
        }

        reference operator*() const { return *m_ptr; }
        reference operator[](Index i) const { return *(m_ptr + i * m_incr.value()); }
        pointer operator->() const { return m_ptr; }

        pointer_based_stl_iterator& operator++()
        {
            m_ptr += m_incr.value();
            return *this;
        }
        pointer_based_stl_iterator& operator--()
        {
            m_ptr -= m_incr.value();
            return *this;
        }

        pointer_based_stl_iterator operator++(int)
        {
            pointer_based_stl_iterator prev(*this);
            operator++();
            return prev;
        }
        pointer_based_stl_iterator operator--(int)
        {
            pointer_based_stl_iterator prev(*this);
            operator--();
            return prev;
        }

        friend pointer_based_stl_iterator operator+(const pointer_based_stl_iterator& a, Index b)
        {
            pointer_based_stl_iterator ret(a);
            ret += b;
            return ret;
        }
        friend pointer_based_stl_iterator operator-(const pointer_based_stl_iterator& a, Index b)
        {
            pointer_based_stl_iterator ret(a);
            ret -= b;
            return ret;
        }
        friend pointer_based_stl_iterator operator+(Index a, const pointer_based_stl_iterator& b)
        {
            pointer_based_stl_iterator ret(b);
            ret += a;
            return ret;
        }
        friend pointer_based_stl_iterator operator-(Index a, const pointer_based_stl_iterator& b)
        {
            pointer_based_stl_iterator ret(b);
            ret -= a;
            return ret;
        }

        pointer_based_stl_iterator& operator+=(Index b)
        {
            m_ptr += b * m_incr.value();
            return *this;
        }
        pointer_based_stl_iterator& operator-=(Index b)
        {
            m_ptr -= b * m_incr.value();
            return *this;
        }

        difference_type operator-(const pointer_based_stl_iterator& other) const { return (m_ptr - other.m_ptr) / m_incr.value(); }

        difference_type operator-(const other_iterator& other) const { return (m_ptr - other.m_ptr) / m_incr.value(); }

        bool operator==(const pointer_based_stl_iterator& other) const { return m_ptr == other.m_ptr; }
        bool operator!=(const pointer_based_stl_iterator& other) const { return m_ptr != other.m_ptr; }
        bool operator<(const pointer_based_stl_iterator& other) const { return m_ptr < other.m_ptr; }
        bool operator<=(const pointer_based_stl_iterator& other) const { return m_ptr <= other.m_ptr; }
        bool operator>(const pointer_based_stl_iterator& other) const { return m_ptr > other.m_ptr; }
        bool operator>=(const pointer_based_stl_iterator& other) const { return m_ptr >= other.m_ptr; }

        bool operator==(const other_iterator& other) const { return m_ptr == other.m_ptr; }
        bool operator!=(const other_iterator& other) const { return m_ptr != other.m_ptr; }
        bool operator<(const other_iterator& other) const { return m_ptr < other.m_ptr; }
        bool operator<=(const other_iterator& other) const { return m_ptr <= other.m_ptr; }
        bool operator>(const other_iterator& other) const { return m_ptr > other.m_ptr; }
        bool operator>=(const other_iterator& other) const { return m_ptr >= other.m_ptr; }

    protected:
        pointer m_ptr;
        internal::variable_if_dynamic<Index, XprType::InnerStrideAtCompileTime> m_incr;
    };

    template <typename _XprType> struct indexed_based_stl_iterator_traits<generic_randaccess_stl_iterator<_XprType>>
    {
        typedef _XprType XprType;
        typedef generic_randaccess_stl_iterator<typename internal::remove_const<XprType>::type> non_const_iterator;
        typedef generic_randaccess_stl_iterator<typename internal::add_const<XprType>::type> const_iterator;
    };

    template <typename XprType> class generic_randaccess_stl_iterator : public indexed_based_stl_iterator_base<generic_randaccess_stl_iterator<XprType>>
    {
    public:
        typedef typename XprType::Scalar value_type;

    protected:
        enum
        {
            has_direct_access = (internal::traits<XprType>::Flags & DirectAccessBit) ? 1 : 0,
            is_lvalue = internal::is_lvalue<XprType>::value
        };

        typedef indexed_based_stl_iterator_base<generic_randaccess_stl_iterator> Base;
        using Base::m_index;
        using Base::mp_xpr;

        // TODO currently const Transpose/Reshape expressions never returns const references,
        // so lets return by value too.
        //typedef typename internal::conditional<bool(has_direct_access), const value_type&, const value_type>::type read_only_ref_t;
        typedef const value_type read_only_ref_t;

    public:
        typedef typename internal::conditional<bool(is_lvalue), value_type*, const value_type*>::type pointer;
        typedef typename internal::conditional<bool(is_lvalue), value_type&, read_only_ref_t>::type reference;

        generic_randaccess_stl_iterator() : Base() {}
        generic_randaccess_stl_iterator(XprType& xpr, Index index) : Base(xpr, index) {}
        generic_randaccess_stl_iterator(const typename Base::non_const_iterator& other) : Base(other) {}
        using Base::operator=;

        reference operator*() const { return (*mp_xpr)(m_index); }
        reference operator[](Index i) const { return (*mp_xpr)(m_index + i); }
        pointer operator->() const { return &((*mp_xpr)(m_index)); }
    };

    template <typename _XprType, DirectionType Direction> struct indexed_based_stl_iterator_traits<subvector_stl_iterator<_XprType, Direction>>
    {
        typedef _XprType XprType;
        typedef subvector_stl_iterator<typename internal::remove_const<XprType>::type, Direction> non_const_iterator;
        typedef subvector_stl_iterator<typename internal::add_const<XprType>::type, Direction> const_iterator;
    };

    template <typename XprType, DirectionType Direction>
    class subvector_stl_iterator : public indexed_based_stl_iterator_base<subvector_stl_iterator<XprType, Direction>>
    {
    protected:
        enum
        {
            is_lvalue = internal::is_lvalue<XprType>::value
        };

        typedef indexed_based_stl_iterator_base<subvector_stl_iterator> Base;
        using Base::m_index;
        using Base::mp_xpr;

        typedef typename internal::conditional<Direction == Vertical, typename XprType::ColXpr, typename XprType::RowXpr>::type SubVectorType;
        typedef typename internal::conditional<Direction == Vertical, typename XprType::ConstColXpr, typename XprType::ConstRowXpr>::type ConstSubVectorType;

    public:
        typedef typename internal::conditional<bool(is_lvalue), SubVectorType, ConstSubVectorType>::type reference;
        typedef typename reference::PlainObject value_type;

    private:
        class subvector_stl_iterator_ptr
        {
        public:
            subvector_stl_iterator_ptr(const reference& subvector) : m_subvector(subvector) {}
            reference* operator->() { return &m_subvector; }

        private:
            reference m_subvector;
        };

    public:
        typedef subvector_stl_iterator_ptr pointer;

        subvector_stl_iterator() : Base() {}
        subvector_stl_iterator(XprType& xpr, Index index) : Base(xpr, index) {}

        reference operator*() const { return (*mp_xpr).template subVector<Direction>(m_index); }
        reference operator[](Index i) const { return (*mp_xpr).template subVector<Direction>(m_index + i); }
        pointer operator->() const { return (*mp_xpr).template subVector<Direction>(m_index); }
    };

    template <typename _XprType, DirectionType Direction> struct indexed_based_stl_iterator_traits<subvector_stl_reverse_iterator<_XprType, Direction>>
    {
        typedef _XprType XprType;
        typedef subvector_stl_reverse_iterator<typename internal::remove_const<XprType>::type, Direction> non_const_iterator;
        typedef subvector_stl_reverse_iterator<typename internal::add_const<XprType>::type, Direction> const_iterator;
    };

    template <typename XprType, DirectionType Direction>
    class subvector_stl_reverse_iterator : public indexed_based_stl_reverse_iterator_base<subvector_stl_reverse_iterator<XprType, Direction>>
    {
    protected:
        enum
        {
            is_lvalue = internal::is_lvalue<XprType>::value
        };

        typedef indexed_based_stl_reverse_iterator_base<subvector_stl_reverse_iterator> Base;
        using Base::m_index;
        using Base::mp_xpr;

        typedef typename internal::conditional<Direction == Vertical, typename XprType::ColXpr, typename XprType::RowXpr>::type SubVectorType;
        typedef typename internal::conditional<Direction == Vertical, typename XprType::ConstColXpr, typename XprType::ConstRowXpr>::type ConstSubVectorType;

    public:
        typedef typename internal::conditional<bool(is_lvalue), SubVectorType, ConstSubVectorType>::type reference;
        typedef typename reference::PlainObject value_type;

    private:
        class subvector_stl_reverse_iterator_ptr
        {
        public:
            subvector_stl_reverse_iterator_ptr(const reference& subvector) : m_subvector(subvector) {}
            reference* operator->() { return &m_subvector; }

        private:
            reference m_subvector;
        };

    public:
        typedef subvector_stl_reverse_iterator_ptr pointer;

        subvector_stl_reverse_iterator() : Base() {}
        subvector_stl_reverse_iterator(XprType& xpr, Index index) : Base(xpr, index) {}

        reference operator*() const { return (*mp_xpr).template subVector<Direction>(m_index); }
        reference operator[](Index i) const { return (*mp_xpr).template subVector<Direction>(m_index + i); }
        pointer operator->() const { return (*mp_xpr).template subVector<Direction>(m_index); }
    };

}  // namespace internal

/** returns an iterator to the first element of the 1D vector or array
  * \only_for_vectors
  * \sa end(), cbegin()
  */
template <typename Derived> inline typename DenseBase<Derived>::iterator DenseBase<Derived>::begin()
{
    EIGEN_STATIC_ASSERT_VECTOR_ONLY(Derived);
    return iterator(derived(), 0);
}

/** const version of begin() */
template <typename Derived> inline typename DenseBase<Derived>::const_iterator DenseBase<Derived>::begin() const { return cbegin(); }

/** returns a read-only const_iterator to the first element of the 1D vector or array
  * \only_for_vectors
  * \sa cend(), begin()
  */
template <typename Derived> inline typename DenseBase<Derived>::const_iterator DenseBase<Derived>::cbegin() const
{
    EIGEN_STATIC_ASSERT_VECTOR_ONLY(Derived);
    return const_iterator(derived(), 0);
}

/** returns an iterator to the element following the last element of the 1D vector or array
  * \only_for_vectors
  * \sa begin(), cend()
  */
template <typename Derived> inline typename DenseBase<Derived>::iterator DenseBase<Derived>::end()
{
    EIGEN_STATIC_ASSERT_VECTOR_ONLY(Derived);
    return iterator(derived(), size());
}

/** const version of end() */
template <typename Derived> inline typename DenseBase<Derived>::const_iterator DenseBase<Derived>::end() const { return cend(); }

/** returns a read-only const_iterator to the element following the last element of the 1D vector or array
  * \only_for_vectors
  * \sa begin(), cend()
  */
template <typename Derived> inline typename DenseBase<Derived>::const_iterator DenseBase<Derived>::cend() const
{
    EIGEN_STATIC_ASSERT_VECTOR_ONLY(Derived);
    return const_iterator(derived(), size());
}

}  // namespace Eigen

#endif  // EIGEN_STLITERATORS_H
